Article
Licensed
Unlicensed Requires Authentication

Structural water in ferrihydrite and constraints this provides on possible structure models

  • , , , , and EMAIL logo
Published/Copyright: April 2, 2015
Become an author with De Gruyter Brill
Author Information
American Mineralogist
From the journal American Mineralogist Volume 96 Issue 4

Abstract

The dry thermal transformation of 2-line ferrihydrite to hematite was investigated using combinations of thermogravimetric (TG) and differential scanning calorimetric (DSC) analysis, along with in situ DSC and pair distribution function (PDF) analysis of X-ray total scattering data and in situ temperature controlled infrared (IR) spectroscopy. TG data show a 25.6 ± 0.1% weight loss below 300 °C, ascribed to the removal of surface water since PDF analysis shows no change in the structure of ferrihydrite up to this temperature. The transformation to hematite occurs at around 415 ± 1 °C (peak temperature) at a heating rate of 10 °C/min, with no obvious weight change during or after the transformation. In situ PDF analysis indicates that the ferrihydrite bulk structure remained intact up to the direct transition to crystalline hematite, with no intermediate phases, crystalline or amorphous, formed. In situ IR data shows the extent of absorption attributable to OH stretching in ferrihydrite at 215 °C dropped to 10% of its room-temperature value. These results suggest ferrihydrite contains very little structural OH: the molar ratio of OH/Fe is 0.18 ± 0.01. A recently proposed akdalaite-like ferrihydrite model has an OH/Fe equal to 0.2, consistent with this result. The 3-phase model proposed by Drits et al. (1993) has an average formula close to FeOOH, with an OH/Fe equal to 1.0, far more than suggested by our experiments. Based on the constraints set by the estimated water content and the PDF signatures, we examined possible anion packing types and local structural motifs in ferrihydrite, and demonstrate that ABAC is the only feasible packing type and that a peak at 3.44(2) Å in PDF provides indirect evidence for the presence of tetrahedral Fe.

Keywords : Ferrihydrite; hydrous ferric oxide; hydroxyl; hematite; goethite; pair distribution function; PDF analysis; tetrahedral iron in ferrihydrite
Received: 2009-11-16
Accepted: 2010-10-27
Published Online: 2015-4-2
Published in Print: 2011-4-1

© 2015 by Walter de Gruyter Berlin/Boston

Articles in the same Issue

  1. Roebling Medal Lecture. The three partners of metamorphic petrology
  2. Relationship between structure, morphology, and carbon isotopic composition of graphite in marbles: Implications for calcite-graphite carbon isotope thermometry
  3. Crystal structure, mosaicity, and strain analysis of Hawaiian olivines using in situ X-ray diffraction
  4. Characterization of deep weathering and nanoporosity development in shale—A neutron study
  5. Structural water in ferrihydrite and constraints this provides on possible structure models
  6. Critical evaluation of the revised akdalaite model for ferrihydrite
  7. Neutron diffraction study of hydrogen in birnessite structures
  8. Pressless split-sphere apparatus equipped with scaled-up Kawai-cell for mineralogical studies at 10–20 GPa
  9. Dislocation microstructures in majorite garnet experimentally deformed in the multi-anvil apparatus
  10. Density of carbonated peridotite magma at high pressure using an X-ray absorption method
  11. Stability and bulk modulus of Ni3S, a new nickel sulfur compound, and the melting relations of the system Ni-NiS up to 10 GPa
  12. Far-infrared spectra of synthetic [4][(Al2-xGax)(Si2–yGey)](OH,OD,F)2-kinoshitalite: Characterization and assignment of interlayer Ba-Oinner and Ba-Oouter stretching bands
  13. High-temperature elasticity of polycrystalline orthoenstatite (MgSiO3)
  14. Anatomy of a metabentonite: Nucleation and growth of illite crystals and their coalescence into mixed-layer illite/smectite
  15. Zn-O tetrahedral bond length variations in normal spinel oxides
  16. A new thermodynamic analysis of the intergrowth of hedenbergite and magnetite with Ca-Fe-rich olivine
  17. Raman spectroscopic investigations of some Tl-sulfosalt minerals containing pyramidal (As,Sb)S3 groups
  18. A first record of strong structural relaxation of TO4 tetrahedra in a spinel solid solution
  19. The high-pressure behavior of orthorhombic amphiboles
  20. XAS determination of the Fe local environment and oxidation state in phonolite glasses
  21. Chemical variation and significance of micas from the Fregeneda-Almendra pegmatitic field (Central-Iberian Zone, Spain and Portugal)
  22. Light-induced molecular change in HgI2·As4S4: Evidence by single-crystal X-ray diffraction and Raman spectroscopy
  23. Low-temperature electron paramagnetic resonance studies on natural calumetite from Khetri copper mine, Rajasthan, India
  24. Chromatite and its Cr3+- and Cr6+-bearing precursor minerals from the Nabi Musa Mottled Zone complex, Judean Desert
  25. Hazenite, KNaMg2(PO4)2⋅14H2O, a new biologically related phosphate mineral, from Mono Lake, California, U.S.A.
  26. The fractional latent heat of crystallizing magmas
https://doi.org/10.2138/am.2011.3460
Keywords for this article
Ferrihydrite; hydrous ferric oxide; hydroxyl; hematite; goethite; pair distribution function; PDF analysis; tetrahedral iron in ferrihydrite

Articles in the same Issue

  1. Roebling Medal Lecture. The three partners of metamorphic petrology
  2. Relationship between structure, morphology, and carbon isotopic composition of graphite in marbles: Implications for calcite-graphite carbon isotope thermometry
  3. Crystal structure, mosaicity, and strain analysis of Hawaiian olivines using in situ X-ray diffraction
  4. Characterization of deep weathering and nanoporosity development in shale—A neutron study
  5. Structural water in ferrihydrite and constraints this provides on possible structure models
  6. Critical evaluation of the revised akdalaite model for ferrihydrite
  7. Neutron diffraction study of hydrogen in birnessite structures
  8. Pressless split-sphere apparatus equipped with scaled-up Kawai-cell for mineralogical studies at 10–20 GPa
  9. Dislocation microstructures in majorite garnet experimentally deformed in the multi-anvil apparatus
  10. Density of carbonated peridotite magma at high pressure using an X-ray absorption method
  11. Stability and bulk modulus of Ni3S, a new nickel sulfur compound, and the melting relations of the system Ni-NiS up to 10 GPa
  12. Far-infrared spectra of synthetic [4][(Al2-xGax)(Si2–yGey)](OH,OD,F)2-kinoshitalite: Characterization and assignment of interlayer Ba-Oinner and Ba-Oouter stretching bands
  13. High-temperature elasticity of polycrystalline orthoenstatite (MgSiO3)
  14. Anatomy of a metabentonite: Nucleation and growth of illite crystals and their coalescence into mixed-layer illite/smectite
  15. Zn-O tetrahedral bond length variations in normal spinel oxides
  16. A new thermodynamic analysis of the intergrowth of hedenbergite and magnetite with Ca-Fe-rich olivine
  17. Raman spectroscopic investigations of some Tl-sulfosalt minerals containing pyramidal (As,Sb)S3 groups
  18. A first record of strong structural relaxation of TO4 tetrahedra in a spinel solid solution
  19. The high-pressure behavior of orthorhombic amphiboles
  20. XAS determination of the Fe local environment and oxidation state in phonolite glasses
  21. Chemical variation and significance of micas from the Fregeneda-Almendra pegmatitic field (Central-Iberian Zone, Spain and Portugal)
  22. Light-induced molecular change in HgI2·As4S4: Evidence by single-crystal X-ray diffraction and Raman spectroscopy
  23. Low-temperature electron paramagnetic resonance studies on natural calumetite from Khetri copper mine, Rajasthan, India
  24. Chromatite and its Cr3+- and Cr6+-bearing precursor minerals from the Nabi Musa Mottled Zone complex, Judean Desert
  25. Hazenite, KNaMg2(PO4)2⋅14H2O, a new biologically related phosphate mineral, from Mono Lake, California, U.S.A.
  26. The fractional latent heat of crystallizing magmas
Downloaded on 5.4.2026 from https://www.degruyterbrill.com/document/doi/10.2138/am.2011.3460/html
Scroll to top button